Effect of a chiral dopant on hysteresis phenomena induced by external fields in liquid crystals.

The design and development of functional self-assembled soft matter structures, particularly liquid crystals that adapt responsively to multiple stimuli, are essential for both fundamental scientific research and advanced technological applications. This work investigates how chiral dopant concentration governs the field-induced unwinding and hysteresis behavior of cholesteric liquid crystals (E7 liquid crystal mixture doped with CB15) confined in homeotropic cells. The study measures discrete pitch jumps and pronounced hysteresis loops as a function of dopant concentration in both voltage- and magnetic-field-driven unwinding, providing experimental insight into composition-controlled phase transitions in thin-layer geometries. A critical dopant concentration was identified below which the cholesteric helix does not form due to surface anchoring effects. The critical fields increase with the increase of dopant concentration, and a linear dependence of the magnetic threshold on concentration is demonstrated. Experimental observations are compared with theoretical models for infinite systems, with an emphasis on discrete switching phenomena and threshold behaviors. These results provide new guidelines for designing responsive cholesteric soft materials and electro- and magneto-optical devices that exhibit controllable, stepwise switching.